Device at railway wheels and method for obtaining said device

ABSTRACT

The present invention relates to a device for improving the adhesitivity of surface refined parts (6) to the body (7) of railway wheels (1), which surface refined parts (6) have been produced by treating the railway wheel (1) with high energy generated preferably by laser radiation (8). In order to prevent or at least obstruct the risk for loosening of the surface refined parts (6) from the body (7) of the railway wheel (1), the maximum thickness (B) of the surface refined parts (6) is selected so that the Hertzian pressure which affects the railway wheel (1) when said wheel is loaded with the maximum permitted pressure thereon is substantially carried by the body (7) of the railway wheel (1) beneath the surface refined parts (6).

FIELD OF THE INVENTION

The present invention relates to a device for improving the adhesitivityof surface refined parts to the body of railway wheels, which surfacerefined parts have been produced by treating the railway wheel with highenergy generated preferably by laser radiation.

The present invention also relates to a simple method for obtaining saiddevice.

BACKGROUND OF THE INVENTION

DE, C1, 35 09 582 teaches a railway wheel which has been surface refinedor improved by means of laser radiation. However, the thickness of thesurface refined parts is not maximized and said parts have therefore asubstantial thickness. The results in that there is a great risk thatsaid parts loosen, i.e. that so called flaking out occurs.

The object of the present invention is to avoid this drawback, whichaccording to the invention is arrived at by providing the abovementioneddevice with the characterizing features of the present invention.

SUMMARY OF THE INVENTION

A method for obtaining said device comprises according to the inventionthe characterizing features of the present invention.

Since the device having said characterizing features ensures that theHertzian pressure is substantially carried by the body of the railwaywheel, loosening of the surface refined parts from the body is preventedor obstructed.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention will be further described below with reference to theaccompanying drawings, wherein

FIG. 1 schematically illustrates a railway wheel on a rail;

FIG. 2 schematically illustrates a surface treatment of the railwaywheel carried out in accordance with the method of the invention,whereby said surface treatment is a surface application;

FIG. 3 schematically illustrates a substantial magnification of asection of an area of the railway wheel at which surface application orsurface coating according to FIG. 2 has occured;

FIG. 4 schematically illustrates a surface treatment of the railwaywheel according to the present method, whereby said surface treatment isa surface impregnation;

FIG. 5 illustrates a substantially magnified section of an area of therailway wheel at which surface impregnation according to FIG. 4 hasoccured;

FIG. 6 is an enlarged section of a part of the railway wheel which inaccordance with the method of the invention has been surface treated bysurface application, whereby surface treating strings located besideeach other have been integrated with each other;

FIG. 7 illustrates a section of a part of the railway wheel which inaccordance with the method of the invention has been surface treated bysurface impregnation, whereby surface treating strings located besideeach other are integrated with each other;

FIG. 8 illustrates a section of a part of the railway wheel with afinished surface treatment provided in accordance with the presentmethod, and

FIGS. 9,10,11,12,13 and 14 schematically illustrates parts of railwaywheels on which surface treating strings are applied in accordance withthe method of the invention in various patterns.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS

The railway wheel 1 illustrated in the drawings has a wheel tread 2through which it is adapted to roll or run on a rail 3. The railwaywheel 1 further includes a rail flange 4 which in a manner known per seensures that the wheel can not move laterally relative to the rail 3such that it ends up beside said rail. The railway wheel 1 also includesan arcuate transition portion 5 between the wheel tread 2 and railflange 4. Central parts 5a of this transition part 5 have a smallerradius than the radii of outer parts 5b, 5c on opposite sides of saidcentral parts 5a. When the railway wheel 1 rolls on the rail 3 duringmovement thereof on straight distances, in curves, on climbs, overswitches and so on, it is the transition portion 5, the part 2a of thewheel tread 2 closest to said transition portion 5 and the part 4a ofthe rail flange 4 closest to said transition portion 5, i.e. those parts2a, 5 and 4a located within the wheel sector S, which can be worn downby the rail 3 and/or slide thereagainst and/or generate noise duringsliding thereagainst.

Those parts 2a, 5 and 4a of the railway wheel 1 which are exposed tosaid influence and/or permit said influence, are surface refined orimproved with high energy, preferably laser radiation, whereby a maximumthickness B of the surface refined parts 6 is selected so that theHertzian pressure which affects the railway wheel 1 when said wheel isloaded with the maximum permitted pressure thereon is substantiallycarried by the body 7 of the railway wheel 1 beneath the surface refinedparts 6, whereby loosening of said surface refined parts 6 from saidbody 7 during loading of the railway wheel 1 with the maximum permittedpressure is prevented or obstructed. The maximum thickness of thesurface treated parts 6 is preferably 5 mm, whereby it is ensured thatthe Hertzian pressure affecting the railway wheel 1 when said wheel isloaded with the normally maximum permitted pressure thereon, issubstantially carried by the body 7 of the railway wheel 1 beneath thesurface refined parts 6. To the melt obtained at the surface refinement,at least such a metal, metal alloy or metal mixture and/or at least sucha ceramic is added, which permits that said parts 2a, 5 and 4a are lessworn and/or get better sliding properties and/or give rise to less noisethan what the base material of the body 7 of the railway wheel permits.

With the expression surface refinement or improvement it is here meantsurface coating and/or surface impregnation and/or surface recovery.

This high-energy surface refinement can e.g. be accomplished by applyingthe beam 8 from a laser device (not shown) on said parts 2a, 5 and 4awhile simultaneously adding said metallic materials 9 and/or ceramics 10to the melt obtained by means of the beam 8. Preferably, said metalmaterials 9 as well as ceramics 10 are added to the melt.

Examples of metal materials 9 that can be added to the ment are yttrium,niobium, tantalum, nickel, chromium, cobolt, molybdenum, tin, lead,indium, zirconium, silicon, aluminium, titanium, tungsten or vanadium orat least one metal alloy or metal mixture containing at least one ofthese metals.

Ceramics 10 which can be added to the melt belong e.g. to the groupincluding carbides, nitrides, oxids or borides. At least one such metal9, metal alloy or metal mixture and/or at least one such ceramic 10 canbe added to the melt and/or the surface refinement of the wheel tread 2and the transition portion 5 between the wheel tread 2 and rail flange 4and eventually the rail flange 4 can be conducted in such manner thatthe wheel tread 2 and the transition portion 5 between said wheel tread2 and the rail flange 4 and eventually said rail flange 4 are worn atsubstantially the same rate.

The surface refinement can be carried out locally on the railway wheel 1in such manner that substantial heating of the railway wheel 1 caused bythe surface refinement only occurs locally within a small area inrelation to the total range of the railway wheel 1 in and around thespot of surface refinement, whereby undesired extensive heating andthereby undesired changes of essential portions of the base material ofthe body 7 of the railway wheel 1 are avoided.

The railway wheel 1 can be surface refined while it is mounted on awheel axis, whereby said railway wheel 1 during the surface refinementis cooled preferably with cooling air so that heat generated during saidsurface refinement is prevented from propagating into bearing parts inthe railway wheel 1 and thereby preventing or obstructing unfavourableheating of lubricant present in said bearing parts.

Furthermore, the surface refinement is preferably extended in such a waythat it covers at least parts of the transition portion 5 between thewheel tread 2 and the rail flange 4 and also extends in over at leastparts 2a of the wheel tread 2 and/or parts 4a of the rail flange 4.Hereby, the surface refinement can be extended in such a way that itcovers the entire transition portion 5 between the wheel tread 2 and therail flange 4 and at least the parts 2a, 4a of said wheel tread 2 aswell as said rail flange 4 located closest to said transition portion 5.

Furthermore, the surface refinement can be extended in such a way thatit covers that part 2a of the wheel tread 2, which lies closest to thetransition portion 5 and which is situated at a distance A (see FIG. 8)from a centre point M of the wheel tread 2, whereby the distance A ispreferably 10-20 mm. The surface refinement can also be extended in suchmanner that it covers at least parts of the height H of the rail flange4 between the wheel tread 2 and outer parts 4b of said rail flange 4.Preferably, the surface refinement can be extended such that it isthickest primarily in the central parts 5a of the transition portion 5between the wheel tread 2 and the rail flange 4 and such that it fromits thickest portion at primarily central parts 5a of the transitionportion 5 has a successively decreasing thickness in direction towardsthe centre point M of the wheel tread 2 and the outer parts 4b of therail flange 4.

However, it is often advantageous to surface refine the wheel tread 2along its entire width, the entire transition portion 5 and the railflange 4 all the way up to the outer parts 4b thereof and to aboutcentral portions of said outer parts 4b where said outer parts start toturn down in a direction towards the outer end surface of the railwaywheel 1.

The surface refinement can e.g. be extended from the central parts 5a ofthe transition portion 5 (preferably from the centre of said centralparts 5a) in a direction towards the outer parts 4b of the rail flange 4and thereafter or before in a direction towards the wheel tread 2.

The surface refinement can be extended by locating surface refiningstrings 11 beside each other within an area C extending peripherallyaround the railway wheel 1 in the running direction thereof, so thatsaid railway wheel 1 is in contact with the rail 3 through said surfacerefining strings 11.

Said surface refining strings 11 are shown schematically in the drawingsas thin lines, but they are in fact substantially wider than theselines.

As is apparent from FIGS. 9 and 10, all these surface refining strings11 are located in parallel with a plane or level D extendingperpendicular or substantially perpendicular to the centre axis 12 ofthe railway wheel 1. Furthermore, each surface refining string 11 mayextend around the railway wheel 1 as an endless surface refining ringwhich, seen from the side in radial direction towards the railway wheel1, can be straight.

As is apparent from FIG. 9, the distances between all surface refiningstrings 11 may be the same. As is shown in FIG. 10 however, thedistances between the surface refining strings 11 within the centralparts 5a of the transition portion 5 (i.e. where the radius of thearcuate transition portion 5 is the smallest) can be small, while thedistances between the surface refining strings 11 on the wheel tread 2and/or rail flange 4 are larger and may increase successively in adirection from the central parts 5a of the transition portion 5.

As is apparent from FIG. 11 some of the surface refining strings 11 canbe located peripherally around the railway wheel 1 and in parallel withthe plane D, i.e. perpendicular to the centre axis 12, while othersurface refining strings 11 can be located in parallel with plane E,i.e. at an angle of 30-60° relative to said centre axis 12. From FIG. 12it is also apparent that the surface refining strings 11 running inparallel with the plane D can be located on the transition portion 5 andon the parts 2a and 4a of the wheel tread 2 and rail flange 4respectively, while the surface refining strings 11 running in parallelwith plane or level E can be located on the rail flange 4 close to thepart 4a.

As is apparent from FIGS. 12-14, the surface refining strings 11can--instead of being straight--be wave formed, e.g. have sine-waveshape. Each wave formed surface refining string 11 can be designed as aperipherally around the railway wheel 1 extending surface refining ringand each such surface refining string 11 can extend substantially inparallel with the plane D (see FIG. 12). The wave formed surfacerefining strings can be located at the same or at various relativedistances in the same way as the surface refining strings 11 describedabove in connection with FIGS. 9 and 10. The wave shaped surfacerefining strings 11--and besides also the straight surface refiningstrings 11--can be positioned as "broken", peripherally around therailway wheel 1 extending surface refining ring, as is shown in FIG. 13.Alternatively, the wave formed surface refining strings 11 can belocated such that they extend substantially in parallel with plane E(see FIG. 14).

As is apparent from FIGS. 6 and 7, the surface refining strings 11 canbe located so relative to each other that they extend partly integratedwith each other.

Hereby, the surface refining strings can be integrated with each otherso that a portion F1 of 2-50%, preferably 20-40%, of the width F of asurface refining string 11 is integrated with a portion F1 of 2-50%,preferably 20-40%, of another surface refining string 11, whereby acertain portion F1 of the width F of a surface refining string 11preferably is integrated with as large or substantially as large aportion F1 of the width F of another surface refining string 11. This isillustrated in FIG. 6 and 7, wherein however, the surface of the surfacerefining strings 11 not yet has been smoothed or levelled for obtainingfinal surface smoothness.

As is apparent from FIG. 3, at least a certain part of the railway wheelcan be surface refined by applying on its original surface 13 a material9 and/or 10 which has been added to the melt such that at least portions9a and/or 10a of this material will be located above the originalsurface 13.

As is apparent from FIG. 5, at least another certain part of the railwaywheel 1 can be surface refined by impregnating its original surface 13with the material 9 and/or 10 added to the melt, so that this materialcompletely or that at least the main portion thereof will be locatedbeneath the original surface 13.

The abovementioned application of material 9 and/or 10 on the originalsurface 13 may e.g. occur on the transition portion 5 and the wheeltread 2, while the abovementioned impregnation with material 9 and/or 10of the original surface 13 may e.g. be carried out on the rail flange 4.

During the surface refinement, at least a metal 9, a metal alloy ormetal mixture and/or at least a ceramic 10 can be added to the melt, sothat the added material 9 and/or 10 remains substantially unchanged inthe melt.

Finally, it should be mentioned that the railway wheel 1 can bepreheated before the surface refinement, namely to a temperature above200° C. and that the surface refined parts of the railway wheel 1preferably are ground for obtaining the required surface smoothness andsurface fineness.

The railway wheel 1 can be surface refined in its original design,preferably when it is newly manufactured. Alternatively, a ring (notshown) which is provided, e.g. shrunk-on a railway wheel 1 and adaptedto cover worn parts of the railway wheel 1, is surface refined inaccordance with said method.

The device and method according to the invention is not limited to whatis defined above, but may vary within the scope of the following claims.An alternative example is that the maximum thickness B of the surfacerefined parts 6 in accordance with the requirements set can be 0.5 mmand any other thickness up to 5 mm, eventually increased with 10% at themost.

I claim:
 1. A method for making a railway wheel for rolling on a rail,the railway wheel having a body which includes a tread, a flange, and anarcuate transition portion extending between the tread and the flange,the transition portion having a curved surface, said method comprisingsteps of:selecting a thickness of surface refined parts to be applied toouter surfaces of the body of the railway wheel so that a Hertzianpressure acting on the railway wheel as a result of the railway wheelrolling on the rail is carried by the body lying beneath the surfacerefined parts; preheating the railway wheel to at least 200° C; applyingenergy generated by laser radiation to at least one local area selectedfrom a group consisting of the tread, the flange, and the transitionportion of the body of the railway wheel to create a melt on the outersurfaces of the body while simultaneously adding at least one materialto the melt; cooling the melt and the at least one material to form thesurface refined parts having said thickness on the outer surfaces of thebody of the railway wheel; and machining the surface refined parts toachieve a predetermined surface finish.
 2. The method of claim 1 whereinthe at least one material added to the melt is selected from a groupconsisting of a metal, a metal alloy, a metal mixture, a ceramic, and ametal and ceramic mixture.
 3. The method of claim 1 wherein the surfacerefined parts are formed on the outer surfaces of the body of therailway wheel such that the tread, the flange, and the transitionportion wear at approximately the same rate.
 4. The method of claim 1wherein the surface refined parts areas are formed on the body of therailway wheel when the railway wheel is mounted on a wheel axis, saidstep of cooling the melt and the at least one material is accomplishedusing cooling air to prevent heat generated during said step of applyingenergy from propagating into bearing parts of the railway wheel.
 5. Themethod of claim 1 wherein the surface refined parts have a maximumthickness in a central portion of the transition portion of the body ofthe railway wheel.
 6. The method of claim 5 wherein the surface refinedparts have side thicknesses in the flange and in the tread which areless than the maximum thickness in the central portion of the transitionportion.
 7. The method of claim 1 wherein the surface refined partscomprise a plurality of surface strings extending peripherally aroundthe railway wheel in a direction of travel of the railway wheel, theplurality of surface strings are for engaging the rail.
 8. The method ofclaim 7 wherein at least one of the plurality of surface strings extendsat an angle of between 30° and 60° relative to an axis through a centerof the railway wheel.
 9. The method of claim 7 wherein at least one ofthe plurality of surface strings extends peripherally around the railwaywheel in a wave-shaped pattern.